The document proposes concepts for space-based solar power including collecting sunlight in space via photovoltaic arrays or lasers, transmitting the power to Earth via microwave beams, and using robotics for construction and maintenance. Key aspects are a 15km sun tower that could generate 3GW of power and transmit it to a rectenna on Earth for under 5 cents/kWh. Challenges include developing pointing and structural control for platforms in space, and robotics like legged robots and hyper-redundant systems to enable long-term autonomous operations.
2. Sun Tower Concept
15 kM bed length
3 GW output beam
< 5 cents/kWHr
$125B Fab Estimate
Microwave beam to
earth mounted
“Rectenna”
3. Introduction
Introduction
Laser Beam to Existing Photovoltaic
Solar Array
4. Satellite Concept of Operation
1. Concentrator focuses
sunlight on spacebased
PV array
2. PV array powers laser diode
3. Laser diode pumps fibers
4. Light from fibers is fed to
optics and transmitted to Earth
7. Power is
6. DC electricity distributed to
is converted to AC consumers
5. Terrestrial PV
receiver array converts
sunlight to DC electricity
5. Transmitter Face and Robot
83,841,250 Radiating Elements
Microwave (5.8GHz) 2.141 GW Radiated
•Two robots placed
symmetrically on
transmitter’s frontside
•Robots move on a rail
connected at perimeter
and center
Robot assembles and
repairs transmitter modules
6. Solar Cell Efficiency vs Wavelength
1kW/m2
~ Sun on Earth
Typical earth
mounted solar
array has 14%
efficiency
Visible Light
(reference)
Example: Laser Diode Array achieves 40% with LASER SSP &
Photovoltaic ground Array
7. Economic and Market Factors General Cost Findings
– For 1996, U.S.
• Generating costs for new plants averaged about 3.8 ¢/kWh (EIA, 1997)
– For ~ 2020, U.S.
•A “reference case” for generation costs in 2020 is ~ 3.2 to 3.3 ¢/kWh
– World Bank experts suggested an average generating cost, ~ 2020, for
rapidly growing economics, of ~ 5.5 ¢/kWh
Under following conditions:
• Deregulation of foreign electric power markets
• Resource inputs trade in a world market at world prices
• Globalization of investment and technology
• Interfuel competition holds costs down
10
SSP Economic & Market Analysis Team
8. Preliminary Observations Market
Growth In Electric Capacity Supply
1995 2020 (GW)
695
1,043
1,738
China OECD Other Developing
World Energy Prospects to 2020, IEA, 1998
14
SSP Economic & Market Analysis Team
9. SPG Pointing Accuracy, Structural Control Trades
• Pointing
– Off pointing : % of capture (2 degrees of control)
– Surface accuracy requires active control
– 12o for PV concentrator cells
– Each concentrator needs its own control
– Disturbance while pointing may impact WPT
– Station keeping
• Lifetime (40 yrs)
– Rotating machinery
– Concentrator Materials
– Actuator control
Pat George
10. Robotics
• SSP must be managed by robotics
– Installation
– Perform maintenance
– Affect repairs
• All are imperative to achieve cost
objective of < 5 cents per kWHour
11. LEMUR
Legged Excursion Mechanical Utility Robot
LEMUR
A new type of autonomous npod walker
called LEMUR has been developed for
assembly, inspection, and maintenance.
This robot demonstrates multimode
operations (mobility, inspection, and
manipulation) with a modular and
multifunctional toolset.
LEMUR Configuration – Demonstrated fine manipulation
and tool based operations
– Examined payload identification
Stereo Cameras
methods
– Implemented fiducial markers for
encoding payload identification,
orientation, and characteristics
– Performed visual inspection of
4 DOF Hex Driver Leg
payloads and robots
4 DOF Gripper Leg
w/ inline camera
(Palmcam) 3 DOF Gripper Leg
12. LEMUR
Legged Excursion Mechanical Utility Robot
• Accomplishments
– Designed and integrated LEMUR mobile
platform
– Developed a threefingered manipulator Three
with compliant grasp adjustment for fingered
manipulation of fine/delicate payloads manipulator
with
– Developed a hex driver endeffector with
integrated
retractable foot
camera optics
– Developed a miniature macroscopic
imaging camera (Palmcam) for
integration into grasping manipulator
– Developed algorithms and computer code
for stereo vision and pattern recognition
using wavelet decomposition of fiducials
– Demonstrated visual object and self
inspection using the Palmcam Hex driver with
retractable foot
• Current Work
– Developing software for autonomous
navigation, inspection, and manipulation
of target
14. Hyper Redundant Intelligent Systems
• Benefits
– Highly Redundant (> 7 DOF) serial
link manipulator chains
– Capable of long reach into highly
constrained spaces (trusses,
frames)
– Capable of prehensile grasping,
limbless locomotion
– Redundant to multiple joint failures
• Research Challenges
– Path and motion planning to
arbitrary locations in a complex 3D
structure using generalized voronoi
graph search
15. Assessing Technology Readiness Levels
System Test, Launch
& Operations TRL 9 Actual system “flight proven” through successful
mission operations
System/Subsystem TRL 8 Actual system completed and “flight qualified” through
Development test and demonstration (Ground or Flight)
TRL 7 System prototype demonstration in a space
Technology
environment
Demonstration
TRL 6 System/subsystem model or prototype demonstration
in a relevant environment (Ground or Space)
Technology
TRL 5 Component and/or breadboard validation in relevant
Development
environment
TRL 4 Component and/or breadboard validation in laboratory
Research to Prove
Feasibility environment
TRL 3
Analytical and experimental critical function and/or
Basic Technology
characteristic proofofconcept
Research
TRL 2
Technology concept and/or application formulated
Basic principles observed and reported
TRL 1